# Yii

> Yii is a helper class serving common framework functionalities.

[API reference](/docs/api/index.md) › [Global namespace](/docs/api/global/index.md) › Yii

| class | `Yii` |
| --- | --- |
| Extends | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| Since | 2.0 |
| Source | [`framework/Yii.php`](https://github.com/yiisoft/yii2/blob/22.0/framework/Yii.php#L25) |

Yii is a helper class serving common framework functionalities.

It extends from [`BaseYii`](/docs/api/yii/baseyii/index.md) which provides the actual implementation.
By writing your own Yii class, you can customize some functionalities of [`BaseYii`](/docs/api/yii/baseyii/index.md).

## Properties

| Property | Type | Description | Defined by |
| --- | --- | --- | --- |
| <span id="property-aliases"></span>[`$aliases`](/docs/api/yii/baseyii/index.md#property-aliases) static | `array` | Registered path aliases Default: `['@yii' => __DIR__]`. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="property-app"></span>[`$app`](/docs/api/yii/baseyii/index.md#property-app) static | [`yii\console\Application`](/docs/api/yii/console/application/index.md)`\|`[`yii\web\Application`](/docs/api/yii/web/application/index.md)`<yii\TUserIdentity>\|null` | The application instance Default: `null`. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="property-container"></span>[`$container`](/docs/api/yii/baseyii/index.md#property-container) static | [`yii\di\Container`](/docs/api/yii/di/container/index.md) | The dependency injection (DI) container used by [`createObject()`](/docs/api/yii/baseyii/index.md#method-createObject). Default: `null`. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |

## Methods

| Method | Description | Defined by |
| --- | --- | --- |
| <span id="method-beginProfile"></span>[`beginProfile()`](/docs/api/yii/baseyii/index.md#method-beginProfile) static | Marks the beginning of a code block for profiling. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-configure"></span>[`configure()`](/docs/api/yii/baseyii/index.md#method-configure) static | Configures an object with the initial property values. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-createObject"></span>[`createObject()`](/docs/api/yii/baseyii/index.md#method-createObject) static | Creates a new object using the given configuration. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-debug"></span>[`debug()`](/docs/api/yii/baseyii/index.md#method-debug) static | Logs a debug message. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-endProfile"></span>[`endProfile()`](/docs/api/yii/baseyii/index.md#method-endProfile) static | Marks the end of a code block for profiling. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-error"></span>[`error()`](/docs/api/yii/baseyii/index.md#method-error) static | Logs an error message. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-getAlias"></span>[`getAlias()`](/docs/api/yii/baseyii/index.md#method-getAlias) static | Translates a path alias into an actual path. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-getLogger"></span>[`getLogger()`](/docs/api/yii/baseyii/index.md#method-getLogger) static |  | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-getObjectVars"></span>[`getObjectVars()`](/docs/api/yii/baseyii/index.md#method-getObjectVars) static | Returns the public member variables of an object. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-getRootAlias"></span>[`getRootAlias()`](/docs/api/yii/baseyii/index.md#method-getRootAlias) static | Returns the root alias part of a given alias. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-getVersion"></span>[`getVersion()`](/docs/api/yii/baseyii/index.md#method-getVersion) static | Returns a string representing the current version of the Yii framework. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-info"></span>[`info()`](/docs/api/yii/baseyii/index.md#method-info) static | Logs an informative message. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-setAlias"></span>[`setAlias()`](/docs/api/yii/baseyii/index.md#method-setAlias) static | Registers a path alias. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-setLogger"></span>[`setLogger()`](/docs/api/yii/baseyii/index.md#method-setLogger) static | Sets the logger object. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-t"></span>[`t()`](/docs/api/yii/baseyii/index.md#method-t) static | Translates a message to the specified language. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |
| <span id="method-warning"></span>[`warning()`](/docs/api/yii/baseyii/index.md#method-warning) static | Logs a warning message. | [`yii\BaseYii`](/docs/api/yii/baseyii/index.md) |